Reactor coolant pump auxiliary flexible vacuum seal for reactor coolant system vacuum degasification

ABSTRACT

An auxiliary flexible vacuum seal for preparing a reactor coolant pump for vacuum degasification of the reactor coolant system employs a flexible boot member having a pair of longitudinally-displaced opposite open end portions and a pair of side-by-side longitudinally-extending side portions in the form of flanges defining a split in the boot member along a side thereof and extending between the open end portions for allowing flexing of the boot member between open and closed side configurations to permit its installation and removal on and from the pump. The seal also employs clamping brackets and fasteners for releasably and sealably clamping together the flanges of the boot member at the split to retain the boot member in its closed configuration. The seal further includes a pair of circumferentially-extending sealing portions formed integrally on the interior of the boot member at opposite open end portions thereof for sealably engaging the pump when the boot member is flexed to its closed configuration to thereby permit generation of a vacuum seal condition between the boot member and the pump. Preferably, a boot support member is disposed within the boot member between the boot member and the pump for supporting the boot member when in its closed configuration.

CROSS REFERENCE TO RELATED APPLICATIONS

Reference is hereby made to the following copending applications dealingwith related subject matter and assigned to the assignee of the presentinvention:

1. "Sealing Devices For The Drive Shaft Of A High Pressure Fluid Pump"by Bonhomme, assigned U. S. Serial No. 379,196 and filed May 17, 1982,now U.S. Pat. No. 4,581,076 issued May 6, 1986.

2. "Nuclear Reactor Coolant PUmp Impeller/Shaft Assembly" by L. S.Jenkins, assigned U. S. Serial No. 761,447 and filed Aug. 1, 1985, nowU.S. Pat. No. 4,690,612 issued Sept. 1, 1987.

3. "Improved Shaft Seal" by K. P. Quinn, assigned U.S. Serial No.739,745 and filed May 31, 1985, now U.S. Pat. No. 4,693,481, issuedSept. 15, 1987.

4. "Reactor Coolant Pump Hydrostatic Sealing Assembly With ImprovedHydraulic Balance" by R. F. Guardiani et al, assigned U.S. Serial No.063,331 and filed June 17, 1987, now U.S. Pat. No. 4,838,559, issuedJune 13, 1989.

5. "Reactor Coolant Pump Sealing Surface With Titanium Nitride Coating"by G. Zottola, assigned U.S. Serial No. 035,832 and filed Apr. 8, 1987,now U.S. Pat. No. 4,871,297, issued Oct. 3, 1989.

6. "Reactor Coolant Pump Hydrostatic Sealing Assembly With ExternallyPressurized Hydraulic Balance Chamber" by R. F. Guardiani, assigned U.S.Serial No. 091,224 and filed Aug. 31, 1987, now U.S. Pat. NO. 4,848,774,issued July 1, 1989.

7. "Reactor Coolant Pump Shaft Seal Utilizing Shape Memory Metal" by D.J. Janacko, assigned U.S. Serial No. 197,174 and filed May 23, 1988.

8. "Reactor Coolant Pump Auxiliary Seal For Reactor Coolant SystemVacuum Degasification" by J. D. Fornof, assigned U.S. Serial No. 222,649and filed July 21, 1988.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to shaft seals and, moreparticularly, is concerned with a reactor coolant pump auxiliaryflexible vacuum seal for reactor coolant system vacuum degasification.

2. Description of the Prior Art

In pressurized water nuclear power plants, a reactor coolant system isused to transport heat from the reactor core to steam generators for theproduction of steam. The steam is then used to drive a turbinegenerator. The reactor coolant system includes a plurality of separatecooling loops, each connected to the reactor core and containing a steamgenerator and a reactor coolant pump.

The reactor coolant pump typically is a vertical, single stage,centrifugal pump designed to move large volumes of reactor coolant athigh temperatures and pressures, for example 550 degrees F and 2500 psi.The pump basically includes three general sections from bottom totop--hydraulic, shaft seal and motor sections. The lower hydraulicsection includes an impeller mounted on the lower end of a pump shaftwhich is operable within the pump casing to pump reactor coolant aboutthe respective loop. The upper motor section includes a motor which iscoupled to drive the pump shaft. The middle shaft seal section includesthree tandem sealing assemblies--lower primary, middle secondary andupper tertiary sealing assemblies. The sealing assemblies are locatedconcentric to, and near the top end of, the pump shaft. Their combinedpurpose is to mechanically contain the high positive pressure coolant ofthe reactor coolant system from leakage along the pump shaft to thecontainment atmosphere during normal operating condition. Representativeexamples of pump shaft sealing assemblies known in the prior art are theones disclosed in U.S. Pat. Nos. to MacCrum (3,522,948), Singleton(3,529,838), Villasor (3,632,117), AndreWs et al (3,720,222) and Boes(4,275,891) and in the first three patent applications cross-referencedabove, all of which are assigned to the same assignee as the presentinvention.

Thus, the sealing assemblies in the reactor coolant pumps are designedto hold high positive coolant pressures. This fact has raised someconcerns about possibility of damage being done to the reactor coolantpumps during reactor coolant system vacuum degasification. Proceduresfor vacuum degasification of the reactor coolant system are described inU.S. Pat. No. 4,647,425 to Battaglia et al, which is assigned to thesame assignee as the present invention and is hereby incorporated byreference. Basically, in vacuum degasification of the reactor coolantsystem a vacuum or negative pressure is imposed on the system and thuson the reactor coolant pumps. This, in effect, pressurizes the pumps inreverse. One major concern is that reverse pressurization might draw thewater used to cool the pump sealing assemblies back into the pumpsealing assemblies by a reverse flow of the water through filters whichmight bring back contamination in the form of dirt and foreign matteralong with the water from the filters into the sealing assemblies. Then,when the pumps are restarted after conclusion of vacuum degasification,the sealing assemblies may become damaged by the presence of thecontamination therein.

Consequently, a need exists for an effective way to prevent reversepressurization of the reactor coolant pumps so as to eliminate theseconcerns about possible damage to the pump sealing assemblies.

SUMMARY OF THE INVENTION

The present invention provides a reactor coolant pump auxiliary flexiblevacuum seal designed to satisfy the aforementioned needs. The auxiliaryflexible vacuum seal of the present invention provides a simple andeffective way to prepare the reactor coolant pumps so that the reactorcoolant system can be vacuum degasified without applying a reversepressure to the pump sealing assemblies. The auxiliary flexible vacuumseal is an external, temporary seal that would be installed prior to thestart of vacuum degasification between the pump sealing housing andshaft, and then removed after degasification is completed. The auxiliaryseal accepts the entire reverse pressure, thus preventing any possibledamage to the primary, secondary and tertiary pump sealing assemblies ofthe pump.

The auxiliary flexible vacuum seal of the present invention is analternative to the invention illustrated and described in the eighthpatent application crossreferenced above. The flexible vacuum sealoffers several advantages over the rigid segmented seal of thecross-referenced application. First, the flexible seal is embodiedprimarily in the form of a single flexible split boot member with a pairof axially-spaced integral sealing portions, preferably in the form ofring elements, resulting in fewer parts to handle and less sealinglength to be concerned with. Second, all parts of the flexible seal aredisposable, thus minimizing decontamination and storage requirements.Third, the flexible seal is easier to manipulate within the limitedspace of the motor stand. Fourth, deviations in concentricity betweenthe shaft and seal housing would be of no concern with the flexibleseal. Fifth, the flexible seal fits with the shaft in either itsaxiallydisplaced coupled or uncoupled positions. Sixth, the flexibleseal can be installed without the need to remove any of the parts of thepump other than some piping and associated connections.

Accordingly, the present invention is directed to an auxiliary flexiblevacuum seal useful in a reactor coolant pump for preparing the pump forvacuum degasification of the reactor coolant system. The flexible vacuumseal comprises: (a) a flexible boot member having a pair oflongitudinally-displaced opposite open end portions and a pair ofside-by-side longitudinally-extending side portions defining a split inthe boot member along a side thereof and extending between the open endportions for allowing flexing of the boot member between open and closedside configurations to permit its installation and removal on and fromthe pump; (b) means for releasably and sealably clamping together theside portions of the boot member at the split to retain the boot memberin its closed configuration; and (c) a pair ofcircumferentiallyextending sealably portions on the interior of the bootmember at the opposite open end portions thereof for sealably engagingthe pump when the boot member is installed and flexed to its closedconfiguration to thereby permit generation of a vacuum seal conditionbetween the boot member and the pump.

Further, the flexible seal includes a boot support member disposablewithin the boot member between the boot member and the pump forsupporting the boot member when in its closed configuration. Moreparticularly, the boot support member is annular in shape and composedof a pair of semi-annular parts. The support member also has an uppersurface conformed in shape to that of an intermediate portion of theboot member located between its opposite end portions for engagablysupporting the boot member at its intermediate portion. Further, theboot support member has a lower surface conformed in shape to that ofthe pump for mounting the support member thereon.

The boot member of the flexible seal includes a bowlshaped body havingthe opposite end portions and defining a hollow cavity. The cavity isopen at the opposite end portions and openable at the split defined inthe body by the side portions of the boot member. The sealably engagingportions on the boot member at the opposite open end portions thereofare preferably rings projecting radially inwardly and formed integrallyon the body of the boot member. In the alternative, these sealablyengaging portions may be the interior surface of the boot member itselfat its opposite open end portions. The side portions of the boot memberare in the form of a pair of radially outward-projecting andlongitudinallyextending flanges on the body along opposite sides of thesplit and disposed in side-by-side contacting relation when the bootmember is in its closed configuration. The clamping means of theflexible seal includes a pair of brackets mountable along outer sides ofsaid flanges on the boot member body, and a plurality of fastenersextendible through the brackets and flanges therebetween and beingoperable for drawing the brackets toward one another and withdrawing thebrackets away from one another for clamping and releasing the flanges.

The present invention is also directed to a method of preparing areactor coolant pump for vacuum degasification of a reactor coolantsystem. The preparing method comprises the steps of: (a) sealing a sealhousing of the reactor coolant pump by installing a longitudinally splitboot member about a portion of the seal housing and about a shaftextending through the housing; (b) reversing the pressure of the reactorcoolant system at start of vacuum degasification of the reactor coolantsystem, the sealing of the pump seal housing preventing damage tosealing assemblies therein by the reversing of reactor coolant systempressure; (c) terminating reversing of the reactor coolant systempressure at completion of vacuum degasification of the reactor coolantsystem; and (d) unsealing the pump seal housing of the reactor coolantpump by removing the split boot member. Further, the sealing includesstretching the split boot member.

These and other features and advantages of the present invention willbecome apparent to those skilled in the art upon a reading of thefollowing detailed description when taken in conjunction with thedrawings wherein there is shown and described an illustrative embodimentof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the course of the following detailed description, reference will bemade to the attached drawings in which:

FIG. 1 is a schematic representation of one cooling loop of aconventional nuclear reactor coolant system which includes a steamgenerator and a reactor coolant pump connected in series in a closedcoolant flow circuit with the reactor core.

FIG. 2 is a cutaway perspective view of the shaft seal section of areactor coolant pump, illustrating in an axial sectional form the sealhousing and the lower primary, middle secondary and upper tertiarysealing assemblies which are disposed within the seal housing andsurround the pump shaft in this section of the pump.

FIG. 3 is an enlarged view of the axially sectioned seal housing andsealing assemblies of the reactor coolant pump of FIG. 2.

FIG. 4 is a fragmentary view of an upper portion of the axiallysectioned sealing housing of the reactor coolant pump of FIG. 3,illustrating in elevational form an auxiliary flexible vacuum seal ofthe present invention installed about the pump shaft.

FIG. 5 is an enlarged axial sectional view of a flexible boot member andan annular boot support member of the auxiliary flexible vacuum seal ofFIG. 4, also showing in elevational form an upper coupling hub of thepump on the pump shaft above the seal.

FIG. 6 is an elevational view, partly in axial section, of the annularboot support member of the flexible vacuum seal by itself.

FIG. 7 is a bottom plan view of the boot support member as seen alongline 7--7 of FIG. 6.

FIG. 8 is an enlarged fragmentary elevational view of the flexible bootmember and a pair of clamp members of the flexible vacuum seal of FIG.5.

FIG. 9 is a top plan view of flexible boot member and clamp members asseen along line 9--9 of FIG. 8.

FIG. 10 is an axial sectional view of the flexible boot member of theflexible vacuum seal by itself.

FIG. 11 is a top plan view of the flexible boot member as seen alongline 11--11 of FIG. 10.

FIG. 12 is an enlarged view of the circled portion of the flexible bootmember in FIG. 10, showing an interior upper circumferential sealingring on the boot member.

FIG. 13 is a side elevational view of one of the clamp members of theflexible vacuum seal by itself.

FIG. 14 is an end elevational view of the clamp member as seen alongline 14--14 of FIG. 13.

FIG. 15 is a bottom plan view of the clamp member as seen along line15--15 of FIG. 13.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, like reference characters designate likeor corresponding parts throughout the several views. Also in thefollowing description, it is to be understood that such terms as"forward", "rearward", "left", "right", "upwardly", "downwardly", andthe like, are words of convenience and are not to be construed aslimiting terms.

Prior Art Reactor Coolant Pump

Referring now to the drawings, and particularly to FIG. 1, there isshown a schematic representation of one of a plurality of cooling loops10 of a conventional nuclear reactor coolant system. The cooling loop 10includes a steam generator 12 and a reactor coolant pump 14 seriallyconnected in a closed coolant flow circuit with a nuclear reactor core16. The steam generator 12 includes primary tubes 18 communicating withinlet and outlet plenums 20,22 of the generator. The inlet plenum 20 ofthe steam generator 12 is connected in flow communication with theoutlet of the reactor core 16 for receiving hot coolant therefrom alongflow path 24 of the closed flow circuit. The outlet plenum 22 of thesteam generator 12 is connected in flow communication with an inletsuction side of the reactor coolant pump 14 along flow path 26 of theclosed flow circuit. The outlet pressure side of the reactor coolantpump 14 is connected in flow communication with the inlet of the reactorcore 16 for feeding cold coolant thereto along flow path 28 of theclosed flow circuit.

In brief, the coolant pump 14 pumps the coolant under high pressureabout the closed flow circuit. Particularly, hot coolant emanating fromthe reactor core 16 is conducted to the inlet plenum 20 of the steamgenerator 12 and to the primary tubes 18 in communication therewith.While in the primary tubes 18, the hot coolant flows in heat exchangerelationship with cool feedwater supplied to the steam generator 12 viaconventional means (not shown). The feedwater is heated and portionsthereof changed to steam for use in driving a turbine generator (notshown). The coolant, whose temperature has been reduced by the heatexchange, is then recirculated to the reactor core 16 via the coolantpump 14.

The reactor coolant pump 14 must be capable of moving large volumes ofreactor coolant at high temperatures and pressures about the closed flowcircuit. Although, the temperature of the coolant flowing from the steamgenerator 12 to the pump 14 after heat exchange has been cooledsubstantially below the temperature of the coolant flowing to the steamgenerator 12 from the reactor core 16 before heat exchange, itstemperature is still relatively high, being typically about 550 degreesF. The coolant pressure produced by the pump is typically about 2500psi.

As seen in FIGS. 2 and 3, the prior art reactor coolant pump 14generally includes a pump housing 30 which terminates at one end in aseal housing 32. The pump 14 also includes a pump shaft 34 extendingcentrally of the housing 30 and being sealingly and rotatably mountedwithin the seal housing 32. Although not shown, the bottom portion ofthe pump shaft 34 is connected to an impeller, while a top portionthereof is connected to a high-horsepower, induction-type electricmotor. When the motor rotates the shaft. 34, the impeller within theinterior 36 of the housing 30 circulates the coolant flowing through thepump housing 30 at pressures from ambient to approximately 2500 psicover gas with minimum operating pressure of approximately 200 pluspsig. This pressurized coolant applies an upwardly directed, hydrostaticload upon the shaft 34 since the outer portion of the seal housing 32 issurrounded by the ambient atmosphere.

In order that the pump shaft 34 might rotate freely within the sealhousing 32 while maintaining the 2500 psi pressure boundary between thehousing interior 36 and the outside of the seal housing 32,tandemly-arranged lower primary, middle secondary and upper tertiarysealing assemblies 38,40,42 are provided in the positions illustrated inFIGS. 2 and 3 about the pump shaft 34 and within the pump housing 30.The lower primary sealing assembly 38 which performs most of thepressure sealing (approximately 2250 psi) is of the non-contactinghydrostatic type, whereas the middle secondary and upper tertiarysealing assemblies 40,42 are of the contacting or rubbing mechanicaltype.

Each of the sealing assemblies 38,40,42 of the pump 14 generallyincludes a respective annular runner 44,46,48 which is mounted to thepump shaft 34 for rotation therewith and a respective annular seal ring50,52,54 which is stationarily mounted within the seal housing 32. Therespective runners 44,46,48 and seal rings 50,52,54 have top and bottomend surfaces 56,58,60 and 62,64,66 which face one another. The facingsurfaces 56,62 of the runner 44 and seal ring 50 of the lower primarysealing assembly 38 normally do not contact one another but instead afilm of fluid normally flows between them. On the other hand, the facingsurfaces 58,64 and 60,66 of the runners and seal rings 46,52 and 48,54of the middle secondary and upper tertiary sealing assemblies 40 and 42normally contact or rub against one another.

Because the primary sealing assembly 38 normally operates in afilm-riding mode, some provision must be made for handling coolant fluidwhich "leaks off" in the annular space between the seal housing 32 andthe shaft 34 rotatably mounted thereto. Accordingly, the seal housing 32includes a primary leakoff port 68, whereas leakoff ports 70 accommodatecoolant fluid leakoff from secondary and tertiary sealing assemblies40,42.

Also, the reactor coolant pump -4 has an annular fluid blocking splashguard 72 disposed adjacent to an annular collar 74 attached to the pumpshaft 34. The splash guard 72 is seated within an annular recess 76formed about an upper portion 78 of the seal housing 32. Screws 80 (onlyone of which is shown) threaded into holes 82 tapped in the seal housingportion 78 serve to attach the splash guard 72 to the seal housing 32and retain it in the recess 76 such that an inner periphery 84 of thesplash guard 72 is disposed close to the exterior cylindrical surface 86of the shaft collar 74.

RCP Auxiliary Flexible Vacuum Boot Seal of the Present Invention

In accordance with principles of the present invention, an auxiliaryflexible vacuum seal 88 can be temporarily installed, without thenecessity of removing any parts of the pump 14 other than for somepiping (not shown), to prepare the reactor coolant pump 14 for reactorcoolant system vacuum degasification.

Referring now to FIGS. 4 to 15, the auxiliary flexible vacuum seal 88basically includes a flexible boot member 90, clamping means 92, andupper and lower sealing portions, preferably in the form of ringelements . 94,96 (FIG. 8) on the boot member 90. In the alternative, thesealing portions may be the interior surface of the boot member 90itself at the opposite open end portions thereof since the boot member90 is stretched when so installed. Also, preferably, the seal 88includes a boot support member 98. for allowing flexing of the bootmember between open and closed side configurations to permit itsinstallation and removal on and from the pump.

The flexible boot member 90 of the seal 88 includes a bowl-shaped body100 (FIGS. 5, 7 and 8). The body 100 has a pair oflongitudinally-displaced opposite end portions 100A,100B and defines ahollow cavity 102 (FIG. 10) open at the opposite end portions. The body100 also has a pair of side-by-side longitudinally-extending sideportions in the form of flanges 104 defining a split 106 (FIG. 11) inthe boot member body 100 along a side thereof. The split 106 extendsbetween the open end portions 100A,100B rendering the body 100 openableat the split 106 for allowing flexing of the boot member 90 between openand closed side configurations to permit its: installation and removalon and from the pump housing 30 and shaft 34. The flanges 104 of theboot member 90 project radially outward from and extend longitudinallyalong opposite sides of the longitudinal split 106 in the body 100. Theflanges 104 are disposed in side-by-side contacting relation when theboot member 90 is in its closed configuration as seen in FIGS. 9 and 11and displaced from one another when the boot member 90 is flexed to itsopen configuration.

The clamping means 92 of the flexible vacuum seal 88 are operable forreleasably and sealably clamping together the flanges 104 of the bootmember body 100 at the split 106 to retain the boot member 90 in itsclosed configuration. As seen in FIGS. 8, 9 and 13-15, the clampingmeans 92 of the flexible seal 88 includes a pair of brackets 108,110mountable along outer sides of said flanges 104 on the boot member body100, and a plurality of fasteners 112 extendible through the brackets.The brackets 108,110 have a series of holes 114 therethrough which arealignable with holes 116 through the flanges 104. Also, nuts 118 areattached to the brackets 108,110 at alternating ones of the holes 114therein. The fasteners 112 are insertable through the aligned holes114,116 of the brackets 108,110 and flanges 104. Threading the fasteners112 into the nuts 118 operates to draw the brackets 108,110 toward oneanother clamping the flanges 104 therebetween. Unthreading the fasteners112 from the nuts 118 operates to withdraw the brackets 108,110 awayfrom one another for releasing the flanges 104.

Further, the upper and lower sealably engaging portions 94,96 (best seenin FIGS. 10 and 12) on the boot member body 100 at the opposite open endportions 100A,100B thereof are rings being semi-circular in crosssectionand projecting radially inwardly, howver, as mentioned above, theseengaging portions 94,96 may be the interior surface of the boot memberbody 100. Preferably, the rings 94,96 are formed integrally on theinterior surface of the boot 100 of the boot member 90, extendingcircumferentially about the interior and projecting radially inwardlytherefrom for sealably engaging the pump housing 30 and shaft 34 whenthe boot member 90 is installed and flexed to its closed configuration,as seen in FIGS. 4 and 5. The boot member 90 and the sealably engagingrings 94,96 on the opposite end portions 100A,100B thereof are composedof resilient stretchable material such as PVC. The body 90 is in astretched condition when it is installed and clamped to its closedconfiguration. In such closed configuration, it permits generation of avacuum seal condition between the boot member 90 and the pump housing 30and shaft 34. The body 100 has a port 120 conformable to receive theleakoff 70.

Finally, the boot support member 98 (best seen in FIGS. 5, 6 and 7) ofthe flexible seal 88 is disposable within the boot member 90 between itand the pump housing 30 for supporting the boot member 90 when in itsclosed configuration. And shown in FIG. 4 and 5, the boot support member98 is entirely enclosed and covered by the boot member 90 such that theboot support member 98 merely provides an internal supporting structurefor the boot member 98 but does not need to provide a sealing type ofengagement therewith. More particularly, the boot support member 98 isannular in shape and split at 122 such that the member 98 is composed ofa pair of semi-circular parts 124. The support member 98 also has anupper surface 98A conformed in shape to the relatively smooth surface ofan intermediate portion 100C (FIG. 11) of the boot member body 100 beinglocated between its opposite end portions 100A,100B for engagablysupporting the boot member 90 at its intermediate portion. Further, theboot support member 98 has a lower surface 98B conformed in shape to therelatively interrupted shape of the pump housing 30 for mounting thesupport member 98 thereon.

It is thought that the present invention and many of its attendantadvantages will be understood from the foregoing description and it willbe apparent that various changes may be made in the form, constructionand arrangement of the parts thereof without departing from the spiritand scope of the invention or sacrificing all of its materialadvantages, the form hereinbefore described being merely a preferred orexemplary embodiment thereof.

We claim:
 1. An auxiliary flexible vacuum seal for a reactor coolantpump, said seal comprising:(a) a flexible boot member having a pair oflongitudinally-displaced opposite open end portions and a pair ofside-by-side longitudinally-extending side portions defining a split insaid boot member along a side thereof and extending between said openend portions for allowing flexing of said boot member between open andclosed side configurations to permit its installation and removal on andfrom the pump; (b) means for releasably and sealably clamping togethersaid side portions of said boot member at said split to retain said bootmember in said closed configuration; (c) a pair ofcircumferentially-extending sealing portions on said boot member at saidopposite open end portions thereof for sealably engaging the pump whensaid boot member is flexed to said closed configuration to therebypermit generation of a vacuum seal condition between said boot memberand the pump; and (d) a boot support member disposable within andentirely enclosable and coverable by said boot member between said bootmember and the pump for internally supporting said boot member when inits closed configuration.
 2. The seal as recited in claim 1, whereinsaid boot support member, is annular in shape and composed of a pair ofsemi-annular parts.
 3. The seal as recited in claim 1, wherein said bootsupport member has an upper surface conformed in shape to that of anintermediate portion of said boot member located between its oppositeend portions for engagably supporting said boot member at saidintermediate portion.
 4. The seal as recited in claim 1, wherein saidboot support member has a lower surface conformed in shape to that of acircumferential portion of the pump for mounting said support memberthereon.
 5. The seal as recited in claim 1, wherein said boot member andsaid sealably engaging portions on said opposite end portions thereofare composed of resilient stretchable material.
 6. The seal as recitedin claim 1, wherein said boot member includes a bowl-shaped body havingsaid opposite end portions and defining a hollow cavity, said cavitybeing open at said opposite end portions and openable at said splitdefined in said body by said side portions of said boot member.
 7. Theseal as recited in claim 6, wherein said sealably engaging portions onsaid boot member at said opposite open end portions thereof are ringsprojecting radially inwardly and formed integrally on said body of saidboot member.
 8. The seal as recited in claim 6, wherein said sideportions are in the form of a pair of radially outward-projecting andlongitudinally-extending flanges on said body along opposite sides ofsaid split and disposed in side-by-side contacting relation when saidboot member is in its closed configuration.
 9. The seal as recited inclaim 8, wherein said clamping means includes:a pair of bracketsmountable along outer sides of said flanges on said boot member body;and a plurality of fasteners extendible through said brackets and saidflanges therebetween and being operable for drawing said brackets towardone another and withdrawing said brackets away from one another forclamping and releasing said flanges.
 10. The seal as recited in claim 1,wherein said sealably engaging portions on said boot member at saidopposite open end portions thereof are rings being semicircular incross-section and projecting radially inwardly and formed integrally onsaid boot member.
 11. The seal as recited in claim 10, wherein said bootsupport member is annular in shape and composed of a pair ofsemi-annular parts.
 12. The seal as recited in claim 10, wherein saidboot support member has an upper surface conformed in shape to that ofan intermediate portion of said boot member located between its oppositeend portions for engagably supporting said boot member at saidintermediate portion.
 13. The seal as recited in claim 10, wherein saidboot support member has a lower surface conformed in shape to that ofthe pump for mounting said support member thereon.
 14. In a reactorcoolant pump for a reactor coolant system having a stationary housingwith an annular portion defining an opening and a shaft extendingthrough said housing opening in spaced relation to said housing annularportion, an auxiliary flexible vacuum seal for sealing said housingopening between said housing annular portion and said shaft forfacilitating performance of vacuum degasification procedures on thereactor coolant system, said auxiliary seal comprising:(a) a flexible,stretchable boot member having a bowl-shaped body defining a cavitywhich is open at its opposite longitudinally-displaced end portions,means defining a split in a side of said body extending longitudinallybetween said end portions of said body, and a pair of flanges connectedto said body along opposite sides of said split and projecting radiallytherefrom and extending longitudinally between said end portions of saidbody, said split for allowing flexing of said body to an openconfiguration to permit installation and removal of said boot member atsaid side thereof about and from the rotatable shaft of the pump at oneend portion of said body and the housing portion of the pump at he otherend portion of said body, said split also for allowing flexing of saidbody to a closed configuration about the shaft and housing portion; (b)means for releasably clamping together said flanges on said body of saidboot member to retain said body in said closed configuration, saidclamping means including a pair of brackets mountable along outer sidesof said flanges and a plurality of fasteners extendible through saidbrackets and said flanges therebetween and being operable for drawingsaid brackets toward one anther and withdrawing said brackets away fromone another for clamping and releasing said flanges; and (c)axially-spaced and circumferentially-extending sealing portionsintegrally formed on the interior of said body of said boot member atsaid opposite open end portions thereof for sealably engaging the shaftand housing portion in said closed configuration of said body of saidboot member to permit generation of a vacuum seal condition in the spacewithin said cavity bounded by said body and the housing portion andshaft and between said sealably engaging rings on said body.
 15. Theseal as recited in claim 14, further comprising:(d) a boot supportmember disposable within said cavity of said boot member body betweensaid boot member and the housing portion for supporting said boot memberwhen in its closed configuration.
 16. The seal as recited in claim 15,wherein said boot support member is annular in shape and composed of apair of semi-annular parts.
 17. The seal as recited in claim 15, whereinsaid boot support member has an upper surface conformed in shape to thatof an intermediate portion of said boot member body located between itsopposite end portions for engagably supporting said boot member at saidintermediate portion.
 18. The seal as recited in claim 15, wherein saidboot support member has a lower surface conformed in shape to that ofthe pump housing portion for mounting said support member thereon.